Carbed LS engine stumble problem at 5500RPM!

[Rod P]

Originally Posted by Sieg

Rolling down the highway with GW.....bad/broken valve spring. Careful inspection required!

Originally Posted by 67zo6Camaro

I had a similar problem but with fuel injection. Eventually got worse. I finally found some issues. 1st vacuum leak (mine was at the back of the intake and a major one in the valley at knock sensor. 2nd spark plugs were older but looked good, however, they actually had a slight coat of burnt oil vapor because of the blow through on the PVC system. In addition the gap was worn because of the high revving abuse. and 3rd... bad lifter roller and valve spring. It could not keep up with the RPMs and started to float above 5500 RPMs. The way we drive with redline most all the time, the valve springs do get softer with age.

PS, my diagnostic codes showed multiple miss fires, and occasionally a knock sensor code, and occasionally a cam sensor code. I did leak down test, compression test and spark test before I actually found the vacuum leak.

My 2 cents. good luck.

ARRRGGGG!!! I guess the valve train comes apart, I was told valves springs by some others also! I was just hoping there was an easy button, but I should have known better